fix the *_to_one edit templates to work with sf 2.3 and fix a typo in json

| Q             | A
| ------------- | ---
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | see travis
| Fixed tickets | -
| License       | MIT
| Doc PR        | -

this is fixing the many_to_one and one_to_one form types to actually work with symfony 2.3. one_to_one is used with the sonata_type_admin form type.